Certain 2-isonitrosoalkyl-15,16-dihydropyrenes

ABSTRACT

Photochromic 1,3,6,8-tetra (lower) alkyl-15,16-dimethyl-15, 16dihydropyrenes, substituted in one or both of the 2- and 7position by benzoyl, alkanoyl, alkanoyloxy, cyano, nitro, alkyl, Alpha -hydroxyalkyl, Alpha -acyloxyalkyl, Alpha isonitrosoalkyl, or acylamido groups are prepared via substitution of the parent hydrocarbon. A typical embodiment is 2-isonitrosomethyl-1,3,6,8,15,16-hexamethyl-15,16-dihydropyrene.

United States Patent Hall et al.

[ 1 March 6, 1973 CERTAIN 2-ISONITROSOALKYL-15,l6- DIHYDROPYRENES Inventors: Luther A. R. Hall, Woodcliff Lake, N.J.; John A. Gurney, Tarrytown, N.Y.; Harris B. Renfroe, Montvale,

Assignee: Ciba-Geigy Corporation, Ardsley,

Filed: Oct. 16, 1971 Appl. No.: 81,609

Related US. Application Data Division of Ser. No. 635,287, April 7, 1967, Pat. No. 3,557,218, which is a continuation-in-part of Ser. No. 499,064, Oct. 20, 1965, abandoned.

US. Cl. ..260/566 A Int. Cl ..C07c 131/00 Field of Search ..260/647, 566 A [56] References Cited UNITED STATES PATENTS 3,205,263 9/1965 Stansbury et al. ..260/647 X Primary Examiner-Leland A. Sebastian Attorneyl(arl F. Jorda et a].

[5 7] ABSTRACT 2 Claims, No Drawings CERTAIN 2-lSONlTROSOALKYL-l 5,16- DIHYDROPYRENES CROSS REFERENCE This is a division of copending application, Ser. No. 635,287, filed Apr. 7, 1967, now U.S. Pat. No. 3,557,218, which in turn is a continuation-in-part of copending application Ser. No. 499,064 filed Oct. 20,

' 1965 now abandoned.

DETAILED DESCRIPTION This invention relates to organic compounds reversibly convertible from colored to colorless isomeric forms.

More particularly, this invention pertains to 15,16- dihydropyrenes, which are photochromic. Thus these compounds when exposed to light become colored or colorless depending on their structure, and, when withdrawn from light revert to their original state. These compounds accordingly find application as selfattenuating light valves in articles such as tinted safety glass and headlights for automobiles; infra-red screens, solarium windows, display windows, and automatic curtains; in information retrieval apparatus such as computer memory core devices, toys, photocopying devices, light meters, and the like.

The fundamental pyrene nucleus of the compounds of the present invention is numbered as follows:

The compounds of the present invention are represented by the following formulas:

By the term alkyl, and derivations thereof employing the rootfalk, is meant a branched or straight chained saturated hydrocarbon chain of up to about thirty carbon atoms, or a group containing such a chain. Representative of such alkyl groups are thus methyl, ethyl, propyl, isopropyl, butyl, s-butyl, t-butyl, pentyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, eicosyl, dodosyl, tetracosyl, hexacosyl, octacosyl, triacontyl and the like. When the term alkyl is qualified by the designation lower", there is included branched or straight chain hydrocarbon groups of from one to about six carbon atoms.

The compounds of the present invention are prepared via mono or disubstitution in one or more steps as hereafter described of a trans-15,16-dimethyl- 1,3 ,6,8-tetra( lower)alkyl-l 5 l d-dihydropyrene. Introduction of one or more acyl groups such as benzoyl, acetyl, propionoyl, butanoyl and the like is effected through treatment with the corresponding acid chloride or acid anhydride in the presence of stannic chloride, optionally in an inert, non-aqueous solvent such as methylene chloride, chloroform or the like. Thus for example the acetyl, or other alkanoyl, group is introduced through treatment with acetic anhydride, or other alkanoic acid anhydrides, and stannic chloride. In the case of the formyl, there is preferably employed butyl dichloromethyl ether, and stannic chloride. The butyl dichloromethyl ether may be obtained for exampie from n-butyl formate and phosphorus pentachloride.

Compounds where Q is a-isonitrosoalkyl are obtained through the reaction of the corresponding alkanoyl compounds and hydroxylamine. Treatment of the oxime obtained from the formyl starting material with acetic anhydride yields the corresponding cyano compound.

The requisite starting materials for the present invention may be prepared by procedures described in copending application Ser. No. 499,037, filed Oct. 20, I965, now U.S. Pat. No. 3,390,l92. Briefly in the case of the 15,1 6-dimethyl-l ,3,6,8-tetra(lower)alkyll 5, l 6- dihydropyrene, this involves initial preparation of a 2,6-di(lower)alkyl-3,5-bis-(chloromethyl)-4- methylanisole, such as for example 4,6-bis- (chloromethyl)-2-methoxymesitylene, alternatively named as 2,4,6-trimethyl-3,5-bis- (chloromethyl)anisole. This generally comprises treating a readily available or easily prepared 2,6- di(lower)alkyl-4-methyl-phenol with a methylating agent, such as dimethyl sulfate, followed by introduction of chloromethyl groups into the two remaining un- OCH:

(lower)alkyl I lower)alkyl Oxidation of the [2.2]metacyclophane of FORMU- LA 11 A with ferric chloride or with chromium trioxide and sulfuric acid then yields a tetracyclic bis dienone which is oxidatively dehydrogenated with oxygen in the presence of base. Removal of the dione structure with lithium aluminum hydride and aluminum chloride followed by dehydrogenation with palladium then yields the desired l5,16-dimethyl-l,3,6,8-tetra(lower)alkyl- 15 l 6-dihydropyrene starting material.

The following preparations and examples are given solely for the purpose of illustration and are not to be construed as limitations of this invention, many variations of which are possible without departing from the spirit or scope thereof.

PREPARATION I 1,3 ,6,9, l 5 l 6-l-lexamethyl-l 5, l o-dihydropyrene a. Methoxymesitylene 2,4,6-Trimethylphenol, 29.5 g, 0.217 mol, prepared by the procedure of Hart and Beuhl er, J. Org. Chem., 29, 2397 (1964), sodium hydroxide, 12.6 g, 0.316 mol, dissolved in 126 ml of water, and 19.7 ml of dimethyl sulfate, 0.217 mol, are mixed in a vessel cooled in an ice bath. The temperature is raised'and maintained at 50:1 C for one hour, then 7.50 g of sodium hydroxide in an equal weight of water and 10 ml (0.110 mol) of dimethyl sulfate are added at 3 hour intervals during hours. The product is isolated by extraction of the aqueous reaction mixture with seven 57-ml portions of ether. After washing the ether layer with 25 percent sodium hydroxide and evaporating the ether, the residue is fractionally distilled and 26.9 g of methoxymesitylenc, b.p. 29C/0 .4 0.45 mm, 83% yield, is obtained.

b. Bis(chloromethyl)methoxymesitylene A mixture of methoxymesitylene, 7.4 g, 0.049 mol, paraforthen passed through the stirred suspension which is warmed on a steam bath for 12 to 15 hours. The reaction slurry is then cooled and stirred in an ice bath, the crude product being collected by filtration. The collected solid is broken up and washed several times with water to remove hydrochloric acid, dissolved in methylene chloride and this solution is washed several times with a saturated sodium bicarbonate solution, followed by several washings with brine, dried, clarified with charcoal, and concentrated. The resulting solid is slurried with heptane and collected by filtration. A second washing with heptane yields the produce as white needles, 234.2 g, (72 percent), m.p. 138-139. The analytical sample may be prepared by recrystallization from heptane.

Anal. Calcd for C,,H,,,OC1,: C, 58.31; H, 6.53

Found: C, 58.33; H, 6.39

c. Bis(iodomethyl)methoxymesitylene Bis(chloromethyl)methoxymesitylene, 8.0 g, 0.0324 mol, sodium iodide, g, 0.26 mol, and 400 ml of tetrahydrofuran are refluxed for 6 hours. The reaction solvent is removed by distillation at 15 mm pressure. Methylene chloride, 100 ml, and 300 ml of ice water are added. The aqueous phase, after separation of methylene chloride, is extracted 4 times with 20 ml of methylene chloride. The combined organic layers are percolated through 200 ml of crushed calcium sulfate then treated with decolorizing charcoal. The methylene chloride filtrate is concentrated in a vacuum to'30 ml volume and 55 ml of methanol is added. The precipitate is collected and recrystallized first from toluene, and then from ethyl acetate to yield 9.62 g of bis(iodomethyl)methoxymesitylene, alternatively named as 2,4,6-trimethyl-3,5-bis(chloromethyl)- anisole, m.p. 134-l 38C, 69 percentyield.

maldehyde, 7.82 g, 0.197 mol, lithium chloride, 9.82 g,

0.245 mol, and zinc chloride, 4.80 g, 0.049 mol, is heated to 80C and anhydrous hydrogen chloride is passed in. Addition of gas is continued for S'fihburs at 72' -2C during which time monochloromethylated product, which appears first, is converted to the desired bis chloromethylated product. The reaction mixture then is poured into 100 ml of ice, and the solid material is collected on a filter and washed with water. There is obtained 1 1.5g of bis(chloromethyl)methoxymesitylen e, 94 percent of theory. Recrystallization from ethyl acetate yields 9.05 g of product, m.p. 135-l36C.

Alternatively this product is obtained via the following procedure: To 198 g (1.32 mole) of 2-methoxymesitylene are added with stirring 1400 ml of concentrated hydrochloric acid and 78.4 g (0.87 mole) of strioxane (three mole equivalents formaldehyde); the resulting suspension is stirred at room temperature for 0.5 hours and a slow stream of hydrogen chloride is (d) 4,6,8,l2,l4,16-l-lexamethyl-7,13-dimethoxy[ 2.2]metacyclophane Bis(iodomethyl)methoxymesi tylene, 15 g in 500 ml of dry tetrahydrofuran (THF) is added at 1 drop per second to sodium sand, 20 g, 0.87 mol, suspended in 1 liter of refluxing Tl-lF and 2 g of tetraphenylethylene. The system is stirred under nitrogen with a Vibromixer stirrer. Unreacted sodium is filtered off and the THF is removed by distillation in such a way that the pot temperature remains at or below 25C. The residual solid is dissolved in 250 ml. of methylene chloride. The solution is percolated through 15 g of Florisil, then the methylene chloride is evaporated off leaving a residue, which is dissolved in 30 ml. of hot carbon tetrachloride. The solid which precipitates on cooling is collected and treated with 30 ml. of hot cyclohexane. The cyclohexane solution is cooled and the desired product precipitates. There is obtained 1 1.7 g of crude material, which is chromatographed on alkaline alumina. After rechromatographing, there is obtained 0.73 g of material, m.p. 220-231C:

Alternatively the [2.2]metacyclophane is prepared as follows: A 3 liter three-neck flask equipped with a Vibromixer and condenser is flame-dried while the system is purged with a stream of prepurified nitrogen and allowed to cool under a positive pressure of nitrogen. To the flask are added 200 m1 of dry toluene, 20 g freshly cut sodium pieces and about 10 drops of oleic acid. The oil bath temperature is raised to l30-l40; and, when all sodium has melted, agitation provided by the Vibromixer is carried out for minutes. At the end of this time agitation is stopped, and the sodium sand allowed to cool without stirring. To this mixture is added a solution of 750 mg of tetraphenylethylene in 300 ml. tetrahydrofuran (distilled from lithium aluminum hydride and stored over sodium), a deep red color forming immediately.

A 1 liter Hershberg dropping funnel is attached to the reaction vessel under the same nitrogen pressure and a solution of 30 g of 4,6-bis(chloromethyl)methoxymesitylene in 700 ml. of tetrahydrofuran is added through the funnel at a rate of -25 drops/minute. Throughout the addition, a slow agitation is provided by the Vibromixer. Addition of the first charge is complete in 15 hours and a second charge of 30 g of the bis(chloromethyl) compound in 700 ml of tetrahydrofuran is then added over 15 hours. A few drops of ethanol are next added to destroy the red color and, after standing for several minutes to allow the unreacted sodium to settle, the milky-gray suspension is carefully decanted from most of the unreacted sodium into a large sintered-glass funnel prepared with a tight Supercel pad. The reaction flask and pad are washed with additional tetrahydrofuran and the clear, colorless filtrate was concentrated, yielding a crystalline residue. This residue is dissolved in 300 ml of methylene chloride and this solution is filtered, diluted with 300 ml ether, washed with 300 ml of 6N hydrochloric acid, dried, concentrated to a volume of 300 ml. and applied to a 1.5 inch X24 inch column of dry-packed Florisil absorbent (60- 200 mesh). Of six 300 ml, fractions collected, fractions 2,3, and 4 are combined and recrystallized twice from ethanol/heptane to yield the product as clear, colorless prisms, m.p. 234-235.

Anal. Calcd for C ,,H O,: C, 81.77; H, 9.15

Found: C, 81.71; H, 8.89

e. Bis dienone The product of Step (d) is treated with ferric chloride. A solution of 1.00 g of the metacyclophane in 100 ml of dry chloroform is stirred at room temperature for 3 hours with 3.5 g ferric chloride. A precipitate of a reddish-brown inorganic complex of the bisdienone is formed and this is collected by filtration. This solid is immediately suspended in 100 ml. chloroform and 20 ml. 3 N hydrochloric acid. This suspension is shaken until solution occurs; the chloroform layer is separated, washed with water and concentrated. The reddish brown solid, about 1.2 g, is treated with charcoal in boiling ethanol, filtered, and the ethanolic solution is concentrated to about 20 ml. From the cold solution separates 0.9-1.0 g. ofa yellow solid.

Alternatively this product is prepared as follows: A chromic acid solution is prepared by treating 8.0 g of chromium trioxide with 3 to 4 ml of water followed by 6.4 ml. of sulfuric acid, and dilution with water to a total volume of 30 ml. Fifteen milliliters of this chromic acid solution are added dropwise to a stirred suspension of 6.7 g. (0.019 mole) of 4,6,8,12,l4,l6-hexamethyl-5,13-dimethoxy-[2.2]metacyclophane in 500 ml. of acetone over 15 to 20 minutes. Near completion of the addition, a green pasty precipitate forms which adheres to the side of the flask and stirrer blade. This suspension is stirred for 1.5 hours, during which time the precipitate becomes more solid and begins to break up. This mixture is poured into 1 liter of water and stirred with 500 ml. of methylene chloride; the light yellow organic layer is separated from the green aqueous layer, which is extracted with an additional 150 ml. methylene chloride. The combined extracts yields a crystalline light yellow residue which is washed with acetone and collected by filtration to yield the product, m.p. 341-343. Recrystallization from chloroform raises the melting point to 345-347.

Anal. Calcd for C I-1 0,: C, 81.95; H, 8.13

Found C, 81.71; H, 8.07

f. Quinone The product of Step (e) is treated with oxygen in the presence of sodium hydroxide. A suspension of the bisdienone (190 mg) in a solution of methanol (35 ml), water (15 ml), and sodium hydroxide (2.5 g) is stirred for 12 hours at room temperature. The resulting solution is concentrated under reduced pressure, diluted with water (50 ml), and extracted with 20 ml methylene chloride. The blue aqueous layer is extracted again with solvent, and the combined organic extracts are dried and concentrated. The residue is sublimed at l-200 (0.1 mm). The orange sublimate is dissolved in chloroform, diluted with petroleum ether, and after standing overnight at -10 the resulting crystalline product 175 mg, is collected.

g. Hexaene The product of Step (f) is treated with lithium aluminum hdyride and aluminum chloride. To a solution of 7 g. of aluminum chloride in 120 ml. of ether, 2 g. of powdered lithium hydride is added with stirring and the suspension is boiled under reflux for 2 hours. After cooling, a 90 ml. portion of the clear supernatant is withdrawn, transferred to a reaction flask and cooled to 80.

The quinone of step (f) (300 mg) in 10 ml benzene is added to 200 ml of ether and the suspension added dropwise with stirring to the mixed reducing agent at -80 C over a 2 hour period. The suspension is slowly warmed to room temperature and boiled for 0.5 hour. After destroying the excess reagent with ethyl acetate followed by water, and separation of the ether layer, evaporation under reduced pressure yields a green residue which is unstable to light and air.

h. Dihydropyrene The product of Step (g) is treated with palladium and dehydrogenated. A suspension of 50 mg of 50 percent palladium-charcoal in 25 ml of benzene containing 1 ml of acetone is refluxed for 15 minutes. To this mixture is added 50 mg of the above green solid and heating is continued for 6 hours. The suspension is cooled, filtered, and the residue remaining after removal of solvent is sublimed at /0.l mm, m.p. l84l86C, color change at about 240C. The product may also be purified through slurrying in methanol and recrystallizing from hexane.

EXAMPLE I 2-Acetyl-l ,3,6,8,15,16-hexamethyl-l5 ,16- dihydropyrene To a solution of 500 mg of l,3,6,8,l5,l6-hex amethyl-lS,l-dihydropyrene in 25 ml. methylene chloride is added dropwise over 45 minutes a solution of 0.17 ml of acetic anhydride and 0.10 ml. of stannic chloride in 25 ml of methylene chloride. After 18 hours, the reaction is poured into ice-water and this mixture is stirred until the acetic anhydride has dissolved (2 hours). The aqueous suspension is extracted with methylene chloride/ether and these extracts are washed several times with water, dried, and concentrated. The residue is dissolved in methylene chloride and chrom atographed on silica gel. A green band elutes rapidly which is identified as starting material. A second green band which is 2-acetyl-l ,3,6,8,l5,l6-hexamethyl-l5,lfi-dihydropyrene is eluted with methylene chloride, wt. l45 mg (49%), m.p. 202203. Sublimation at l20l30/0.0l mm raises the melting point to 205-206. I

'Use of excess acetic anhydride (e.g. 0.2 ml with 490 mg of the dihydropyrene starting material) yields 2,7- diacetyl-l ,3 ,6,8,l5,1 6-hexamethyll ,16- dihydropyrene, m.p. 226-227C.

EXAMPLE II 2-Formyl-l,3,6,8,l5,l6-hexamethyl-l5,l6- dihydropyrene l ,3,6,8,15 ,1 -l-lexamethyl-l 5 ,1 -dihydropyrene (956 mg) is dissolved in 50 ml. of dry methylene chloride and to this solution at room temperature are added 0.5 ml. of stannic chloride and 1.0 ml of dichloromethylbutyl ether (3 mole equivalents). The dark green solution is stirred at room temperature for 17 hours and poured into water. The aqueous burgundy red suspension is stirred for minutes and extracted with methylene chloride/ether. These extracts are dried and concentrated, and the residue, in methylene chloride is applied to a silica gel column. A dark maroon band is eluted with 3 percent ethylacetate/methylene chloride. Toward the end of the elution the color changes from burgandy to redbrown, and a second fraction is taken. The main fraction yields 2-formyl-l,3,6,8,l5,l6-hexamethyl-l5,l6- dihydropyrene, m.p. 205207 in about 95 percent yield, and upon recrystallization from methanol yields black-red needles, m.p. 206208.

EXAMPLE III 2-Acetamido-7-formyl-l ,3 ,6,8,1 5 l 6-hexamethyl- 15 l 6-dihydropyrene To a stirred solution of 400 mg. of Z-acetamidol,3,6,8,l5,l-hexamethyl-l5,l6-dihydropyrene in 25 ml of methylene chloride is added 0.2 ml. stannic chloride, followed by 0.4 ml. dichloromethylbutyl ether (two-fold excess). After 3.5 hours, the reaction solution is poured into water. The deep burgundy-red suspension is stirred for 15 minutes and extracted with methylene chloride/ether. These extracts are concentrated, treated with toluene, and reconcentrated to remove traces of acetic acid. After drying in a vacuum oven at 40, the dark maroon residue is chromatographed on silica gel using 50 percent ethyl acetate/heptane as eluting solvent to yield 2-acetamido-7-formylhexamethyldihydropyrene. Recrystallization of this material from methylene chloride/heptane yields the product as a dark maroon solid, m.p. 216-2 1 8".

EXAMPLE IV 2-Cyano-l,3,6,8,l5,l6-hexamethyl-l5,l6- dihydropyrene To a slurry of 257 mg. of 2-formyl-l ,3,6,8,l 5,16-hexamethyl-15,l-dihydrofpyrene in ml. of ethanol is added a solution 0 106 mg of hydroxylamine hydrochloride in 5 ml. of water which has been previously neutralized with sodium carbonate to pH 7-8. This mixture is heated at reflux for 15 minutes and water is then added until crystallization begins. After cooling the mixture in an ice bath, the solid is collected by filtration and dried to yield 2-isonitrosomethyl-' l,3,6,8,15,16-hexamethyl-l5,16-dihydropyrene, m.p. 206-208. i

A mixture of 244 mg. of this oxime and 20 ml. of acetic anhydride is heated at reflux for 15 minutes and then poured into water. This mixture is stirred until the acetic anhydride is dissolved and then extracted with methylene chloride-ether. The extracts are washed with brine, dried, and evaporated. The residue is dissolved in toluene and chromatographed on silica gel, eluting with 1:1 methylene chloridezheptane to yield the product as the initial band, m.p. 2l8-2l9C.

By employing 2-acetyl-l,3,6,8,15,l6 hexamethyll5,l6-dihydropyrene, there is similarly obtained 2-(disonitrosoethyl)-l ,3,6,8,]5,16-hexamethyl-l5 ,16- dihydropyrene which is converted to 2-cyano- 1,3 ,6,8, l 5,1 6,-hexamethyl-l 5,16-dihydropyrene.

EXAMPLE XVI The following formulation is prepared:

Geon l03-EP polyvinyl resin Advastate T 3 stabilizer Stearic acid 2-Acetamido-7-nitro-l,3,6,8,l5,16- 0. hexamethyl- 1 5 l fi-dihydropyrene The dihydropyrene is solvent blended (methylene chloride) with the powdered poly(vinyl chloride) and other additives and the solvent is evaporated. The batch is milled on a two-roll plastics mill for 5 minutes at 350F. The milled sheet is compression molded at 365F. into four 5X5X0.045 inch sheets in a picture frame mold. (Molding cycle: 5 minutes at contact pressure; 45 seconds at 5 tons; 45 secondsat 10 tons; 45 seconds at 15 tons; 45 seconds at 20 tons; then flash quench in cold water.) The colored plastic films clear on exposure to light and darken when left in the dark.

What isclaimed is:

l. A compound of the formula (lower)allry1 lower)alkyl (lower)slkyl I lower)alkyl wherein Q is aisonitroso (lower) alkyl group.

2. A compound according to claim I wherein said compound is Z-isonitrosomethyl-l,3,6,8,l5,l6-hexamethyll 5 l 6-dihydropyrene. 

1. A compound of the formula 